1. Field of the Invention
This invention relates to a semiconductor device manufacturing method and a semiconductor device.
2. Background Art
Recently, with the growing demand for the performance of semiconductor transistors, it has been difficult to improve the performance simply by downscaling the transistors, and new technologies have been under development. In one of such technologies, a silicon nitride film, in which a relatively high internal stress is easily obtained, is formed on the semiconductor substrate so as to cover the gate structure so that the stress is applied to the channel below the gate to increase the carrier mobility (see JP-A-2006-237070(Kokai)).
It is known that the carrier mobility of an n-channel transistor increases when a tensile stress in the channel length direction acts on the channel. When a tensile stress in the channel length direction acts on the channel of the n-channel transistor, the silicon nitride film itself needs to have an internal stress in the shrinking direction. However, the possibility of cracking due to this shrinkage is a concern to be addressed.